Various types of photoacoustic sensors are known to detect gases. These include, Fritz et al., US Patent Application No. 2009/0320561, published Dec. 31, 2009 and entitled “Photoacoustic Cell”; Fritz et al., US Patent Application No. 2010/0027012, published Feb. 4, 2010 and entitled, “Photoacoustic Spectroscopy System”; Fritz et al., US Patent Application No. 2010/0045998, published Feb. 25, 2010 and entitled “Photoacoustic Sensor”; and Tobias, US Patent Application No. 2010/0147051, published Jun. 17, 2010 and entitled, “Apparatus and Method for Using the Speed of Sound in Photoacoustic Gas Sensor Measurements. The above noted published applications have been assigned to the assignee hereof, and are incorporated herein by reference.
Precise and repeatable performance of photoacoustic detectors is preferred. Changes in detector response over a period of time can result in measurements exhibiting variances from those initially determined during manufacture and initial calibration. In some instances this can result in the respective detector drifting out of specification.
User calibration is a partial solution to detector drift. However, not all users have the ability or interest required to carry out field calibration.